In recent years, push switches used for input operation units of various electronic apparatuses are lateral push type that operates when being pushed in a direction parallel to circuit boards onto which the push switches are mounted.
FIGS. 8 and 9 are a sectional view and an exploded perspective view of conventional push switch 500 disclosed in Japanese Patent Laid-Open Publication No. 2001-210176, respectively. Main body portion 2M of case 1 made of resin has a recess 2C having a circular shape opening to the front side. Main body portion 2M has bracket portion 3 unitarily formed on an upper position thereof such that it projects toward the rear side as well as to both the right and left sides. Outer contact 5 and center contact 7 are fixed by insert molding to an inner bottom surface of the recess 2C. Each of terminals connected with outer contact 5 and center contact 7 projects outward from positions around bracket portion 3.
Movable contact 9 of a circular dome shape made of elastic sheet metal is disposed inside the recess 2C with its outer rim, or the lower edge of the dome-like shape in contact with outer contact 5 of case 1. The recess 2C of case 1 is covered with insulation sheet 11 made of insulation film having flexibility, which is attached to a flat area around an outer periphery of the recess 2C from the front side.
Operating element 13 made of resin includes flange portion 13A, pressing portion 13B protruding in the center on a rear surface of flange portion 13A, and operating portion 13C protruding in the center on a front surface of flange portion 13A. Flange portion 13A has a rectangular plate shape in the front view. Operating element 13 is disposed movably in front-to-back direction with the periphery of flange portion 13A being guided by inner surfaces of guide walls extending from outer peripheral corners at the front side of case 1, thereby enabling the rear end of pressing portion 13B to depress the center portion of movable contact 9 backward through insulation sheet 11. Operating portion 13C protrudes forward through an opening in metal cover 15 attached to case 1.
FIGS. 10 and 11 are a perspective view and a sectional view of push switch 500 disposed on circuit board 19, respectively. Circuit board 19 has cutout 17 formed in a side edge thereof. Push switch 500 is disposed with bracket portion 3 placed on circuit board 19 such that main body portion 2M of case 1 is fitted in cutout 17. Push switch 500 is thus mounted on circuit board 19 in this position while terminals are soldered to lands.
When operating portion 13C is pushed backward under this mounted condition, operating element 13 moves horizontally backward while being guided, and causes pressing portion 13B to depress the center portion of movable contact 9 backward through insulation sheet 11. When the depressing force exceeds a predetermined amount, the center portion of movable contact 9 is reversed to have a reversed convex shape in association with a tactile response and comes in contact with center contact 7, and push switch 500 is turned on to connecting electrically between center contact 7 and outer contact 5. At this moment, the direction of the above pushing operation is parallel to the surface of circuit board 19 on which push switch 500 is mounted. Since movable contact 9 is depressed directly toward a direction corresponding to its operational direction by operating element 13 that moves horizontally, an excellent click feeling can be obtained from push switch 500 during the above pushing operation.
When the depressing force is removed from operating portion 13C, the center portion of movable contact 9 flips back to have the original forward convex shape and is removed from center contact 7, and operating element 13 is pushed back through insulation sheet 11 to turn off push switch 500.
Push switch 500 is disposed that main body portion 2M of case 1 is placed in cutout 17. However, there is a growing demand for push switches that can be placed and mounted in the similar manner on side edges of circuit boards not provided with cutouts 17 in order to hold circuit boards 19 to low cost.